X31 and Bus molex connector on Vailant boiler

[dbrb2]

I've noticed that my Vailant boiler has both an PCB edge connector X31, used to connect to a VR33 module, and also a molex connector marked "BUS"

Am I right in thinking the VR33 interfaces to the eBus on the boiler - if so is the X31 connector a copy of the molex connection, with the addition of 2 power lines?

[dty]

Yes. X31 (and X32 if you have it - my EcoFit Pure only has X32) are edge connectors for the VR33 and other "internal" eBus devices. The BUS connector is the basic two-wire connector for other eBus devices. I have my eBus monitor connected to it.

Note that eBus itself is bus-powered. My eBus monitor has no external power - half of it is powered from the two-wire eBus terminals and the other half is powered from the USB bus. I don't know what the extra wires are for on the X31/X32 connectors. It could be that they can supply higher power and/or voltage for accessories.

[bruce_miranda]

I can confirm that the 4 wires are 2 x eBus, 2 x fixed DC voltage. Also the VR33 can be daisy chained as well. So if you have another eBus accessory that needs the X31/X32 edge but that space has been taken by the VR33, then you will notice that the VR33 also has it's own X31 on it to use.

[dbrb2]

I can confirm that the 4 wires are 2 x eBus, 2 x fixed DC voltage. Also the VR33 can be daisy chained as well. So if you have another eBus accessory that needs the X31/X32 edge but that space has been taken by the VR33, then you will notice that the VR33 also has it's own X31 on it to use.

Ah cool - thanks. So the edge connector and the Molex connector, were I to buzz them out, would be connected on the data lines - though obviously the edge connector also has two power lines (24v I'm guessing...)

When using eBus, would the burner, 24vRT and 230v RT pairs all be bridged (not to each other obviously...)

[bruce_miranda]

The VR33 does tell you to bridge the 24V RT and 3-4 together. In my boiler there was no 24V RT terminal, so I needed to experiment with 7-8-9 and bridge 7-8, even though the instructions tell you not to touch those terminals in the UK!

Also the eBUS lines may have diodes on them, so will affect any continuity reading you may take. I know they employ a rectifier circuit which allows for the wires to be interchanged without harm.